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생물 유기분자 유도 실리카 합성실험을 통한 생체내 유무기 복합체 형성이해
기미란,민기하,백승필 한국생물공학회 2019 KSBB Journal Vol.34 No.4
The discovery of the principle molecules involved in biosilicification both in diatoms and sponges brings out a new paradigm for silica synthesis at environmentally benign conditions. Here we introduce the biosynthetic method of silica using organic molecules for the undergraduate students. First, the biosilica synthesized was assessed through both a colorimetric method for quantification of silica and structural analysis by SEM image observation. Next, facile immobilization of an enzyme was demonstrated. Specifically, bovine carbonic anhydrase II (bCAII) was efficiently immobilized within silica matrix by simply adding itself to the reaction mixture containing polyamines and tetramethyl orthosilicate in phosphate buffer, obtaining 97% immobilization to initial amount of bCAII. The immobilized bCAII retained 40% of initial activity at 90℃ whereas free form did less than 10% of initial activity at 70℃ and the total yield from the 5 times reuses of immobilized bCAII was twice that of free bCAII. This experimental content that is hard to find in general biology or biochemistry lab could contribute to students' interest in knowledge expansion and application of new materials.
기미란,박기성,Mohamed A. A. Abdelhamid,백승필 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.2
Efforts to find sustainable and eco-friendly ways to conduct chemical reactions have led to the mimicking of nature. In this study, a new silica polymerization protein that can produce silica in an environmentally friendly manner was developed using cathepsin L-like protein (AqCtL) from Amphimedon queenslandica with a 61% sequence identity to that of silicatein-alpha, which is a natural biosilicifying enzyme. To stabilize the protein structure, heterologously expressed AqCtL in Escherichia coli was mutated into AqCtLSN by changing the amino acid residues responsible for protease cleavage. The insoluble form of AqCtLSN was reconstituted into a soluble protein through the refolding process, displaying silica-condensing activity from silicic acid. AqCtLSN self-assembled, aggregated, and attached to a support in the PBS buffer without losing silica deposition activity. These properties were applied to fabricate a silica-hybrid material using a gelatin-tyramine-alginate cross-linked hydrogel as a scaffold. FT-IR analysis revealed that a silica hybrid material was produced owing to the in situ silicification by AqCtLSN immobilized on the hydrogel. The surface of biosilica mediated by AqCtLSN demonstrated an increase in cell proliferation, alkaline phosphatase activity, and calcium mineral precipitation in the osteogenesis of MC3T3 E1 cells compared to those without biosilica. In conclusion, AqCtLSN, recombinantly expressed in E. coli, is a novel biosilica-forming protein that can be used to produce composites for biomedical applications, especially bone regeneration.
기미란,김사열,홍일화,박진규,Kyung-Sook Hong,Ae-Ri Ji,정규식 한국식품영양과학회 2010 Journal of medicinal food Vol.13 No.3
Lactobacillus paraplantarum KNUC25 strain was isolated from overfermented kimchi, a Korean traditional food. The strain had a broad antimicrobial activity spectrum, from Gram-positive to Gram-negative bacteria. The aim of this study was to evaluate the activity of L. paraplantarum KNUC25 against Helicobacter pylori strains. Judged by a disc agar diffusion method, the anti-H. pylori activity existed in the cell-free supernatants (CFSs) of KNUC25. The mean diameters of growth inhibition by 10, 30, and 60μL of a 15-fold concentrated CFS per disc were 11.2, 17.7, and 23.7mm, respectively. The neutralized CFS lost its anti-H. pylori activity, suggesting that acidic pH in CFS may be responsible for the anti-H. pylori activity. Adherence was determined by urease activity of H. pylori adhered to gastric epithelial cell line AGS cells after co-incubation of AGS cells with CFS and H. pylori strain ATCC43504 (s1m1vacA/cagA+), ATCC51932 (s2m2vacA/cagA−), or SS1 (s2m2vacA/cagA+) in vitro followed by three washes by means of centrifugation with saline. Adherence of ATCC43504 or SS1 to AGS cells was reduced by about 70% after a 30-minute incubation with 30μL of a 15-fold concentrated KNUC25 CFS, whereas that of ATCC51932 to AGS cells was not. The results show KNUC25 CFS is effective in inhibiting the growth of H. pylori, which is related to pH and the adherence of cagA-positive H. pylori to gastric cells.
임수진,정대원,기미란,박승필,최유성 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.1
Chitosan/gelatin and chitosan/gelatin/nanohydroxyapatite hydrogels were rapidly and stably prepared without any crosslinking materials by using an engineered tyrosinase (mTyr-CNK) with high catalytic activity for tyrosine/ DOPA-tethered polymeric biomaterials throughout a broad pH range. A dual-barrel syringe with one part containing chitosan/mTyr-CNK solution and the other containing gelatin solution with/without nanohydroxyapatite was successfully used to form homogeneous hydrogels at room temperature followed by 37 oC to simulate an in situ injection approach. The obtained hydrogels exhibited an average pore size greater than 150 m and high swelling ratios with similar mechanical properties to other chemically crosslinked chitosan/gelatin hydrogels. The in vitro degradation properties and cellular viability suggested that the hydrogels could be used as biodegradable and biocompatible scaffolds for biomedical applications, such as space filling biomaterials and delivery vehicles for bioactive molecules and cells. These results demonstrated that mTyr-CNK-mediated hydrogels have remarkable promise as an injectable scaffold biomaterial.